This invention relates to heddle selecting and positioning selected heddles for drawing-in of warp threads in a drawing-in machine. More particularly, the invention relates to the selection and positioning of duplex heddles.
A set of duplex heddles consists of two banks of heddles disposed on either side of the center plane of a heddle frame. The banks of heddles are generally supported on parallel upper and lower heddle bars associated with the heddle frame, the heddle bars being common to both banks of heddles. Typically, the central portions of the heddles of one bank are disposed in front of the center plane of the heddle frame and the central portions of the heddles of the other bank are disposed behind the center plane. The front and rear heddles are alternately arranged on the heddle bars. In order to accomplish drawing the warp threads through the heddles it is necessary to individually select the heddles from a group of unthreaded heddles and then successively position the selected heddles for drawing-in warp threads. A typical way to perform the selection is to provide key hole slots in the central portion of the heddles and a rotatable release key extending through the heddles and adapted to release a heddle when the key is aligned with a key hole in a heddle. A selection mechanism of this type is described in Frederick L. Wienecke's U.S. Pat. No. 3,103,056. A disadvantage of this type of selection is that it requires a separate release key for each bank of heddles. Furthermore, in some applications it is desirable to use very thin, lightweight heddles. For example, in high speed looms it is necessary to reduce the weight of the moving elements as much as possible, in order to attain efficient operation. One way to accomplish this is to use lightweight heddles. Such thin heddles are too narrow to have a key hole as previously described and thus this type of selection cannot be used.
In positioning a heddle for drawing-in after selection, a turning worm is usually employed which turns the central portion of the heddle so that the heddle eye is properly aligned for penetration by the warp drawing-in needle. Wienecke U.S. Pat. No. 3,103,056 shows a turning worm which turns a heddle and holds it against a needle guide. A problem which has been evident, particularly with thin heddles having relatively small eyes, is that it is possible to have misalignment between the heddle eye and the needle since the heddle is retained in place only below the eye. Erwin C. Kieke's U.S. Pat. No. 2,230,494 shows a mechanism which engages heddles above and below the eye with the engaging elements operating on opposite sides of the heddle. But the mechanism is such that it is possible for a heddle to move laterally with respect to at least one of the engaging elements. Also, it does not provide sufficiently positive positioning at the heddle eye to insure proper alignment between the eyes of heddles and the drawing-in needle, particularly with respect to thin heddles, which allow for only a small clearance between the needle and the walls of the heddle eye.